1. Field of the Invention
The present invention relates to a substrate coated with a transparent conductive film, such as indium oxide with tin doped therein (ITO), to be used for a liquid crystal display apparatus, a solar battery or the like, and to a method for manufacturing the coated substrate.
2. Description of Related Art
A substrate such as a glass substrate which has a transparent conductive film deposited thereon, such as ITO, zinc oxide (ZnO) and tin oxide (SnO2), is used for a display apparatus such as an LCD (Liquid Crystal Display) and an EL (Electro Luminescence) apparatus, a photovoltaic apparatus such as a solar battery and an optical sensor, a semi-conductor apparatus such as a TFT (Thin Film Transistor), and an optical communication apparatus such as a light modulator and an optical switch.
In particular, the ITO film, which has properties of high visible spectrum transmission and low resistivity, is widely used as a transparent electrode of a flat-panel display such as a liquid crystal display element, a solar battery or the like.
Conventionally, an ITO film is deposited on a glass substrate by vacuum evaporation coating or sputtering, at a substrate temperature between 300 and 400xc2x0 C. When a transparent conductive film is deposited by DC (Direct Current) sputtering, DC magnetron sputtering, RF (Radio Frequency) magnetron sputtering or the like, the substrate and film are exposed to plasma of sputtering gas such as rare gas. Consequently, there may arise a problem that the substrate and film are damaged by high speed particles and negative ions in plasma colliding with or entering the substrate and film, and thereby the formed film has physical properties of high resistivity and low transmission. In order to evade the above problem a film is deposited at a substrate temperature between 300 and 400xc2x0 C., since it is believed that this method leads to preferable crystallinity, and thereby to low resistivity and high transmission of the obtained film.
In recent years, there is need for a film deposition art for depositing a transparent conductive film on a film including an organic material, such as a polymer film, deposited on a glass substrate. Moreover, needed is a film deposition art for depositing a transparent conductive film on a substrate made of an organic material, such as polyimide, which is selected for the purpose of reduction of device weight. There is, however, a problem that, when the substrate includes an organic material, the substrate temperature cannot be raised to 300 through 400xc2x0 C. in order to evade decomposition of the organic material which has a low temperature limit for heat-resistance in vacuum. Being deposited at a low temperature, a film or a substrate including an organic material is damaged by plasma and the crystallinity of a transparent conductive film deposited thereon is lowered, causing undesirable physical properties of the film or substrate. Caused as a result is deterioration in quality of the substrate coated with a transparent conductive film.
Moreover, required is a flatter transparent conductive film to be deposited on a substrate, which constructs a luminous element such as an EL element, a component for optical communication such as a light modulator and an optical switch, or the like. For instance, according to a thin film EL element which has a transparent conductive film, an insulating layer, a luminescent layer, another insulating layer and an Al electrode deposited on a glass substrate in this order, roughness of the surface of the transparent conductive film causes roughness of the surface of each layer formed thereon, prevents uniform light emission from the luminescent layer, and causes dielectric breakdown due to an electric field which is not applied uniformly. In order to solve the above problems, flat transparent conductive film has been desired.
The present invention has been made with the aim of solving the above problem, and it is an object thereof to provide a substrate coated with a transparent conductive film and a manufacturing method thereof, in which a film with low resistivity, high transmission and preferable flatness is deposited on a film or substrate including an organic material, without damaging the organic material.
Another object of the invention is to provide a substrate coated with a transparent conductive film with still higher transmission and lower resistivity, which can be used for a flat-panel display such as an liquid crystal display element, a solar battery or the like.
Still another object of the invention is to provide a method for manufacturing a substrate coated with a transparent conductive film by which proper oxidation level of metal is achieved, and the obtained transparent conductive film has high transmission, low resistivity and preferable flatness.
A substrate coated with a transparent conductive film according to the present invention comprises a substrate and a transparent conductive film including an oxide of metal or alloy, which film is deposited on the substrate, wherein the transparent conductive film is deposited by: disposing a substrate and a target including metal or alloy in a film deposition chamber; leading an ion beam of rare gas into the film deposition chamber, to cause collision of the ion beam with the target, sputtering-emission of constitutive atoms of the target, and supply of the emitted atoms to the substrate; and leading oxide gas including oxygen radicals as a main element thereof into the film deposition chamber.
The substrate indicates a glass substrate, a flexible substrate including an organic material such as polyimide, or the like. The substrate coated with a transparent conductive film indicates a coated substrate having a transparent conductive film deposited directly on a substrate, or a coated substrate having a transparent conductive film deposited on another film formed on a substrate. The substrate coated with a transparent conductive film further includes a coated substrate having two transparent conductive films deposited on both sides of a substrate, not only one transparent conductive film deposited on one side of the substrate. Moreover, the oxide gas indicates oxygen radicals, oxygen ions, oxygen gas, nitrogen dioxide gas or the like, or mixed gas including such matter.
The transparent conductive film on the substrate is deposited by leading an ion beam of rare gas into the film deposition chamber by ion beam sputtering. Since the substrate and film are not exposed to plasma in the deposition process, the invention can avoid a situation that high speed particles and negative ions in plasma collide with or enter the substrate and film, damaging the film. Moreover, since the oxide gas including oxygen radicals as a main element thereof which is supplied to the substrate has high reactivity, a transparent conductive film on a proper oxidation level can be deposited at a room temperature. Consequently, the deposited film has preferable physical properties of low resistivity and high transmission. Moreover, since the film is not damaged by plasma, the film can be deposited at a room temperature and deposition speed is preferably slow, the invention does not cause roughness on the surface of the transparent conductive film and preferable flatness of the surface can be achieved. Furthermore, it is possible to deposit a transparent conductive film on a substrate including an organic material which is damaged at a high temperature.
For the substrate coated with a transparent conductive film according to the present invention, the oxide gas may be generated through electron cyclotron resonance.
In this substrate coated with a transparent conductive film, the oxide gas of which includes still more oxygen radicals, proper oxidation level of the metal is achieved and physical properties of the transparent conductive film is enhanced.
In the substrate coated with a transparent conductive film according to the present invention, the transparent conductive film may be deposited on a film including an organic material, which film is deposited on the substrate.
In this substrate coated with a transparent conductive film, since a film can be deposited at a room temperature, the transparent conductive film can be deposited on a film including an organic material which is damaged at a high temperature.
In the substrate coated with a transparent conductive film according to the present invention, the substrate may be a glass substrate.
This substrate coated with a transparent conductive film having a preferable quality, in which the substrate is a glass substrate, can be used for a display apparatus such as an LCD and an EL apparatus, a photovoltaic apparatus such as a solar battery and an optical sensor, a semi-conductor apparatus such as a TFT, an optical communication apparatus such as a light modulator and an optical switch, or the like. For instance, when this substrate coated with a transparent conductive film is applied to an EL element, each layer formed on a transparent conductive film deposited on a substrate has a flat surface and light is emitted uniformly from a luminescent layer. Moreover, since an electric field is applied uniformly, dielectric breakdown seldom occurs.
In the substrate coated with a transparent conductive film according to the present invention, the transparent conductive film may be an indium oxide film with tin doped therein.
This substrate coated with a transparent conductive film, which has still higher transmission and lower resistivity, can be used for a flat-panel display such as a liquid crystal display element, a solar battery or the like.
Another substrate coated with a transparent conductive film according to the present invention comprises a substrate and a transparent conductive film including an oxide of metal or alloy, which film is deposited on the substrate, wherein the transparent conductive film is deposited by: disposing a substrate and a target including an oxide of metal or alloy in a film deposition chamber; leading an ion beam of rare gas into the film deposition chamber, to cause collision of the ion beam with the target, sputtering-emission of atoms or molecules constituting the target, and supply of the emitted atoms or molecules to the substrate; and leading oxide gas including oxygen gas or oxygen radicals as a main element thereof into the film deposition chamber.
Since the film on the substrate is deposited by leading an ion beam of rare gas into the film deposition chamber, the substrate and film are not exposed to plasma in the deposition process. Consequently, the film is not damaged, and a transparent conductive film on a proper oxidation level can be deposited at a room temperature. As a result, the deposited film has preferable physical properties of low resistivity and high transmission. Moreover, preferable flatness of the surface can be achieved. Furthermore, it is possible to deposit a transparent conductive film on a film or substrate including an organic material which is damaged at a high temperature.
For the substrate coated with a transparent conductive film according to the present invention, the oxide gas may be generated through electron cyclotron resonance.
In this substrate coated with a transparent conductive film, the oxide gas of which includes still more oxygen radicals, physical properties of the deposited transparent conductive film is further enhanced.
A method for manufacturing a substrate coated with a transparent conductive film according to the present invention is a method for depositing a transparent conductive film including an oxide of metal or alloy on a substrate by: disposing a substrate and a target including metal or alloy in a film deposition chamber; leading an ion beam of rare gas into the film deposition chamber, to cause collision of the ion beam with the target, sputtering-emission of constitutive atoms of the target, and supply of the emitted atoms to the substrate; and leading oxide gas including oxygen radicals as a main element thereof into the film deposition chamber.
Since it is possible to deposit a film in higher vacuum in the manufacturing method than in usual sputtering, the amount of gas entering the film can be reduced and high reactivity is obtained. Moreover, since an ion beam of rare gas is lead into the film deposition chamber and the substrate and film are not exposed to plasma in the deposition process, the invention can avoid a situation that high speed particles and negative ions in plasma collide with or enter the substrate and film, damaging the film. Furthermore, since the oxide gas including oxygen radicals as a main element thereof which is supplied to the substrate has high reactivity, a transparent conductive film on a proper oxidation level can be deposited at a room temperature, without raising the substrate temperature. Consequently, obtained is a substrate coated with a transparent conductive film with preferable physical properties of low resistivity and high transmission. Moreover, since the film is not damaged by plasma, the film can be deposited at a room temperature, deposition speed is preferably slow and the film is deposited in high vacuum, the invention does not cause roughness on the surface of the transparent conductive film and preferable flatness of the surface can be achieved.
As described above, by the manufacturing method of the invention capable of depositing a transparent conductive film with preferable physical properties at a room temperature, it is possible to deposit a transparent conductive film on a film or substrate including an organic material.
In the method for manufacturing a substrate coated with a transparent conductive film according to the present invention, the oxide gas may be generated through electron cyclotron resonance using microwaves.
In this manufacturing method, since the oxide gas includes still more oxygen radicals, proper oxidation level of the metal is achieved and physical properties of the transparent conductive film is further enhanced.
In the method for manufacturing a substrate coated with a transparent conductive film according to the present invention, microwave power for generating the electron cyclotron resonance may be limited to 200 W or higher.
In this manufacturing method, obtained transparent conductive film has still higher transmission, lower resistivity and preferable flatness. Though existence of many oxygen vacancies in the transparent conductive film causes decrease of transmission and increase of resistivity, high microwave power seems to realize high transmission and low resistivity of the transparent conductive film, since high microwave power leads to high radical concentration in oxide gas and proper oxidation level of metal.
In the method for manufacturing a substrate coated with a transparent conductive film according to the present invention, microwave power for generating the electron cyclotron resonance may be limited to 300 W or higher.
In this manufacturing method, the obtained transparent conductive film has still higher transmission, lower resistivity and preferable flatness.
A method for manufacturing a substrate coated with a transparent conductive film according to the present invention is a method for depositing a transparent conductive film including an oxide of metal or alloy on a substrate by: disposing a substrate and a target including an oxide of metal or alloy in a film deposition chamber; leading an ion beam of rare gas into the film deposition chamber, to cause collision of the ion beam with the target, sputtering-emission of atoms or molecules constituting the target, and supply of the emitted atoms or molecules to the substrate; and leading oxide gas including oxygen gas or oxygen radicals as a main element thereof into the film deposition chamber.
Since it is possible to deposit a film in higher vacuum in the manufacturing method than in usual sputtering, the amount of gas entering the film can be reduced and high reactivity can be obtained. Moreover, since an ion beam of rare gas is lead into the film deposition chamber and the substrate and film are not exposed to plasma in the deposition process, the film is not damaged, and a transparent conductive film on a proper oxidation level can be deposited at a room temperature, without raising the substrate temperature. Consequently, obtained is a substrate coated with a transparent conductive film with preferable physical properties of low resistivity and high transmission. Moreover, since the film is not damaged by plasma, the film can be deposited at a room temperature, deposition speed is preferably slow and the film is deposited in high vacuum, the invention does not cause roughness on the surface of the transparent conductive film and preferable flatness of the surface can be achieved.
Consequently, a transparent conductive film with preferable physical properties can be deposited at a room temperature, and hence, it is possible to deposit a transparent conductive film on a film or substrate including an organic material.
In the method for manufacturing a substrate coated with a transparent conductive film according to the present invention, the oxide gas may be generated through electron cyclotron resonance using microwaves.
In this manufacturing method, since the oxide gas includes still more oxygen radicals, physical properties of the deposited transparent conductive film is further enhanced.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.